1. Field of the Invention
The present invention relates to a method for curing a UV (Ultraviolet) curable resin, and in particular to a method for curing a UV-curable resin and a method for packaging an OLED (Organic Light-Emitting Diode).
2. The Related Arts
An organic light-emitting diode or an organic light-emitting diode display (OLED), which is also referred to as an organic electroluminescent diode, is a new technology of display that has been developed since the middle of the twentieth century. Compared to liquid crystal displays, the organic electroluminescent diode possesses a variety of advantages, including full solid state, active emission of light, high brightness, high contrast, being ultra thin, low cost, low power consumption, fast response, wide view angle, wide range of operation temperature, being easy for flexible displaying.
Referring to FIG. 1, an organic electroluminescent diode generally comprises: a substrate 100, a light-emitting element 300 formed on the substrate 100, and a packaging cover 500 laminated on the substrate 100. The light-emitting element 300 comprises an anode 302 formed on the substrate 100, an organic function layer 304 formed on the anode 302, and a cathode 306 formed on the organic function layer 304. The substrate 100 and the packaging cover 500 are laminated together by means of a UV-curable resin 700 that is disposed therebetween and cured in order to hermetically enclose the light-emitting element 300 between the substrate 100 and the packaging cover 500 so that the organic function layer 304 of the light-emitting element 300 is protected against deterioration caused by invasion of humidity.
The organic function layer of the conventional organic electroluminescent diode is generally composed of three function layers, which are respectively a hole transport layer (HTL), an emissive layer (EML), and an electron transport layer (ETL). Each of these layers can be a single layer or a combination of at least one layer. For example, the hole transport layer is sometimes further separated into a hole injection layer and a hole transport layer and the electron transport layer can be further separated into an electron transport layer and an electron injection layer; however, the functions thereof are close and are collectively referred to as “hole transport layer” and “electron transport layer”.
The common practice of the conventional organic electroluminescent diode adopted is glass packaging and both UV-curable resin package or glass resin package require a process of curing of the UV-curable resin. However, in the process of illuminating and curing a UV-curable resin with a UV light, the temperature of the glass substrate may also be raised. Excessively high temperature (exceeding the Tg point of the organic material) may result in property change of the organic material of the organic electroluminescent diode so as to affect the performance of the organic electroluminescent diode product. Thus, it is generally desired to keep the temperature of the glass substrate relatively low during the UV curing operation.
However, in an actual UV curing process, the stacked glass substrate, UV filter, and even flexible substrate (such as a polyethylene naphthalate (PEN) film) provided for flexible displaying, may require an extended time of UV irradiation in order to achieve a desired accumulated light quantity for curing the UV-curable resin at the transmittance of the UV band. Under this condition, the temperature of the glass substrate may get a remarkable rise and the OLED organic material may be affected.
For example, referring to FIG. 2, a temperature curve of a glass substrate is shown for OLED packaging with direct irradiation. In the plot, the irradiance of the UV light is 100 mw/cm2 and after direction irradiation of the UV light for 180 seconds, the maximum temperature of the glass substrate is 90° C. This may result in deterioration of the OLED organic material and thus affect the quality of the OLED.